Unit -1 Operating System Concepts
INDEX
Overview
1.1.Evolution of Operating System & History
1.2.Need of an Operating System
1.3.Single User & Multi User Operating System
- 1.3.1 Types of OS and their advantages and dis-advantages
- 1.3.2 Batch OS, Distributed OS, Multi-Tasking OS
- 1.3.3 Rea-time OS, Mobile OS
1.4.Elements of an Operating System
1.5.Operating System as a Resource Manager
Evolution and History of Operating Systems
Introduction.
An operating system (OS) is a fundamental component of computing that manages hardware, software, and user interactions.
The evolution of operating systems has been driven by advancements in computer technology, increasing complexity, and the need for improved efficiency.
Over time, operating systems have evolved from simple batch processing systems to modern multi-user, multi-tasking, and real-time systems.
1. First Generation (1940s – Early 1950s) – No Operating System.
Early computers, such as ENIAC and UNIVAC, operated without an OS.
Programs were written directly in machine code and manually loaded into the system.
Computers used vacuum tubes and required manual input, making them slow and inefficient.
2. Second Generation (1950s – Early 1960s) – Batch Processing Systems.
Introduction of punch cards for input and magnetic tapes for storage.
Batch processing allowed jobs to be grouped together and executed sequentially.
Computers still lacked interactive user interfaces and multitasking capabilities.
Examples: IBM 704, UNIVAC II.
3. Third Generation (Mid-1960s – 1970s) – Multiprogramming and Time-Sharing.
Introduction of multiprogramming, allowing multiple programs to run simultaneously.
Time-sharing systems enabled multiple users to interact with the computer at the same time.
Development of high-level programming languages like COBOL and FORTRAN improved software development.
4. Fourth Generation (1980s – 1990s) – Personal Computing and GUI.
The rise of personal computers (PCs) led to the development of user-friendly operating systems.
Graphical User Interfaces (GUIs) replaced command-line interfaces, making computers accessible to non-technical users.
Networking capabilities and the concept of distributed computing emerged.
Examples: MS-DOS (1981), Windows 95, Mac OS.
5. Fifth Generation (2000s – Present) – Modern Operating Systems.
Multitasking, multiprocessing, and multi-user capabilities became standard.
Real-time operating systems (RTOS) were developed for mission-critical applications.
Mobile operating systems like Android and iOS transformed the way people use computers.
Cloud computing, artificial intelligence (AI), and virtualization became key trends in OS development.
Examples: Windows 10, Linux, macOS, Android, iOS.
Need of an Operating System.
Introduction.
An operating system (OS) is essential software that acts as an interface between computer hardware and users.
It manages hardware resources, executes applications, and provides a user-friendly environment.
Without an OS, operating a computer would require manual handling of complex processes, making it difficult for users to interact with the system effectively.
Importance and Need for an Operating System.
1. Resource Management
The OS efficiently manages hardware resources like CPU, memory, storage, and input/output devices.
It allocates resources to different applications based on priority, ensuring smooth operation.
2. Process Management
Manages multiple tasks (processes) running on a system.
Uses scheduling techniques to ensure fair distribution of CPU time among different processes.
Prevents conflicts and ensures efficient execution of applications.
3. Memory Management
Allocates memory to programs and deallocates it when no longer needed.
Prevents memory wastage and optimizes system performance.
Handles virtual memory to extend available RAM using disk space.
4. File Management
Organizes, stores, retrieves, and protects files and directories.
Provides access control to prevent unauthorized modifications.
Supports different file systems like NTFS, FAT, and ext4.
5. User Interface and Interaction
Provides a graphical user interface (GUI) or command-line interface (CLI) for user interaction.
Enables users to run applications, access files, and configure system settings easily.
6. Device Management
Controls and coordinates hardware components like printers, keyboards, and storage devices.
Uses device drivers to communicate between the OS and hardware.
Ensures smooth data transfer between devices and the system.
7. Security and Access Control
Protects system data from unauthorized access, malware, and cyber threats.
Implements user authentication (passwords, biometrics) to ensure data security.
Provides encryption, firewall protection, and access control mechanisms.
8. Networking and Communication
Enables data exchange between computers through wired and wireless networks.
Supports protocols like TCP/IP for internet connectivity.
Manages network resources and ensures secure data transmission.
9. Error Detection and Handling
Detects system errors and hardware failures to prevent data loss.
Logs system activities and alerts users about potential issues.
Automatically recovers from minor failures to maintain system stability.
10. Support for Multitasking and Multi-User Environments
Allows multiple applications to run simultaneously (multitasking).
Supports multiple users accessing the system at the same time (multi-user capability).
Ensures efficient resource distribution in shared environments.
Single User & Multi User Operating System.
Single-User & Multi-User Operating Systems and Their Types.
1. Single-User & Multi-User Operating Systems
1.1 Single-User Operating System
A single-user operating system is designed to support only one user at a time.
It allows one person to run applications and perform tasks without interference from other users.
Advantages:
Simplicity and ease of use.
Requires fewer system resources.
Efficient for personal computing.
Disadvantages:
Cannot handle multiple users simultaneously.
Limited resource-sharing capabilities.
Examples: MS-DOS, Windows (Home Editions), macOS (for personal use).
1.2 Multi-User Operating System
A multi-user operating system allows multiple users to access the system simultaneously.
It is commonly used in servers, mainframes, and cloud computing environments.
Advantages:
Efficient resource allocation among users.
Supports remote access and networking.
Enhances productivity in organizations.
Disadvantages:
Requires more system resources.
Security concerns due to multiple users accessing the system.
Examples: UNIX, Linux (Server Editions), Windows Server.
1.3 Types of Operating Systems and Their Advantages & Disadvantages
1.3.1 Classification of Operating Systems.
Operating systems can be categorized based on their functionality and purpose.
| Type of OS | Advantages | Disadvantages |
|---|---|---|
| Batch OS | Automates execution of tasks, improves efficiency | No user interaction, debugging is difficult |
| Distributed OS | Shares resources across multiple computers, enhances performance | Complex setup, security challenges |
| Multi-tasking OS | Allows multiple tasks to run simultaneously, improves productivity | Consumes more memory and CPU resources |
| Real-Time OS (RTOS) | Provides immediate response, suitable for critical applications | Expensive and complex to develop |
| Mobile OS | Optimized for mobile devices, provides touch-friendly UI | Limited hardware compatibility, battery constraints |
1.3.2 Batch OS, Distributed OS, Multi-Tasking OS
Batch Operating System
Groups similar jobs and executes them without user intervention.
Used in early mainframes and in modern automated processing systems.
Example: IBM’s batch processing systems.
Distributed Operating System
Connects multiple systems to work as a single unit.
Used in cloud computing and server environments.
Example: Google’s distributed systems, Apache Hadoop.
Multi-Tasking Operating System
Runs multiple applications simultaneously by managing CPU time efficiently.
Found in most modern personal computers and mobile devices.
Example: Windows, Linux, macOS.
1.3.3 Real-Time OS & Mobile OS
Real-Time Operating System (RTOS)
Processes data in real-time, ensuring immediate response.
Used in mission-critical applications like aviation, healthcare, and robotics.
Examples: VxWorks, QNX, FreeRTOS.
Mobile Operating System
Designed for smartphones, tablets, and handheld devices.
Optimized for touchscreens, battery life, and mobile connectivity.
Examples: Android, iOS.
1.4.Elements of an Operating System.
Introduction.
An operating system (OS) is a vital software component that manages computer hardware and software resources while providing essential services for user applications.
It consists of several key elements that work together to ensure smooth and efficient operation.
These elements include process management, memory management, file system management, device management, user interface, and security mechanisms.
1. Process Management
The OS is responsible for creating, scheduling, and terminating processes.
It ensures that multiple processes can run efficiently without conflicts.
Uses scheduling algorithms like First-Come-First-Serve (FCFS), Shortest Job Next (SJN), and Round Robin to allocate CPU time.
Functions of Process Management:
Process creation and termination.
CPU scheduling and resource allocation.
Synchronization between multiple processes.
2. Memory Management
Manages system memory (RAM) and allocates space to applications and processes.
Uses techniques like paging, segmentation, and virtual memory to optimize memory utilization.
Functions of Memory Management:
Allocating and deallocating memory as needed.
Managing virtual memory for efficient execution of large programs.
Preventing memory leaks and fragmentation.
3. File System Management
The OS organizes, stores, retrieves, and protects files and directories.
Provides access control to ensure data security and integrity.
Functions of File System Management:
Creating, reading, writing, and deleting files.
Managing different file formats and storage structures (e.g., FAT, NTFS, ext4).
Controlling file permissions for users and processes.
4. Device Management
Manages input and output (I/O) devices such as printers, keyboards, and storage drives.
Uses device drivers to communicate between the OS and hardware components.
Functions of Device Management:
Detecting and configuring devices.
Managing data transfer between devices and the CPU.
Handling errors and ensuring device compatibility.
5. User Interface
Allows users to interact with the computer through a graphical user interface (GUI) or command-line interface (CLI).
Provides essential tools for users to execute commands and manage files.
Types of User Interfaces:
CLI (Command-Line Interface): Uses text-based commands (e.g., Linux Terminal, Windows Command Prompt).
GUI (Graphical User Interface): Uses icons, windows, and menus for user interaction (e.g., Windows, macOS).
6. Security and Access Control
Ensures data protection against unauthorized access, malware, and cyber threats.
Implements authentication mechanisms like passwords, encryption, and firewalls.
Functions of Security Management:
User authentication and access control.
Protection against viruses and unauthorized intrusions.
Implementing encryption techniques for secure communication.
Operating System as a Resource Manager.
Introduction.
An operating system (OS) serves as a resource manager by efficiently managing hardware and software resources.
These resources include the CPU, memory, storage devices, input/output devices, and software applications.
The OS ensures that multiple processes can run smoothly without conflicts while optimizing system performance.
Functions of an Operating System as a Resource Manager
1. CPU Management
The OS allocates CPU time to different processes using scheduling techniques such as First-Come-First-Serve (FCFS), Shortest Job Next (SJN), and Round Robin Scheduling.
It ensures fair distribution of processing power among applications.
Handles process execution, switching between tasks as needed.
2. Memory Management
Allocates memory to running programs and deallocates it when no longer needed.
Uses paging, segmentation, and virtual memory to optimize memory utilization.
Prevents memory leaks and fragmentation, ensuring efficient memory usage.
3. File System Management
Organizes and manages files on storage devices.
Controls access permissions to ensure data security.
Maintains file structures and directories for efficient storage and retrieval.
4. Device Management
Coordinates input/output (I/O) devices like printers, keyboards, and disk drives.
Uses device drivers to communicate with hardware components.
Manages data transfer between devices and applications.
5. Process Management
Manages multiple running processes and their execution.
Handles process creation, execution, and termination.
Prevents conflicts between processes through synchronization mechanisms.
6. Security and Access Control
Protects system resources from unauthorized access and cyber threats.
Implements user authentication, encryption, and firewall protection.
Ensures data privacy through role-based access control.
7. Network Resource Management
Manages data transmission across networks.
Ensures proper allocation of bandwidth and network connectivity.
Supports communication between multiple devices over the internet.
Importance of OS as a Resource Manager
Ensures efficient utilization of system resources.
Prevents resource conflicts and deadlocks.
Enhances system performance and reliability.
Provides a secure environment for data processing.